Here's all the reasons it won't be a partner:
1 - We don't have a partner direct since October 2020.
2 - The partners direct only existed because of covid time contratual obligations with third parties, since they had to show third party games but most of the 1st party games were delayed
3 - There were no general directs in 2020, and do you really believe a company would prefer to show their game in a partner direct than in a general one?
4 - There's still a lot of 1st party things to show, such as Grezzo's new game and the rumoured Metroid Prime Trilogy, and they wouldn't hold that to the september direct.
5 - Sony will have a 1st party showcase one day before the direct, they wouldn't let Sony just straight up obstruct all of their information. If it was a partner direct in the same week as a big Sony event, all eyes would be on Sony.
6 (BONUS) - The reception to the partner showcases were VERY negative, there would be A LOT of backlash if another one happened